1) Field of the Invention:
The present invention relates generally to agricultural implements, and, more specifically, to a lift and depth control systems for such implements.
2) Related Art:
Most available multi-frame implements such as field cultivators and chisel plows use a hydraulic cylinder system to provide depth control during field-working operations and adequate ground clearance during transport. Some depth control systems such as shown in U.S. Pat. No. 3,663,032 use rephasing cylinders connected in series to raise and lower the frames in unison. A flow control valve on the towing vehicle extends or retracts the series connected cylinders in unison. The cylinder capacities and strokes must usually be carefully matched for proper cylinder operation. Also, leakage across the ram seals of one or more of the cylinders causes the cylinders to get out of phase, which results in uneven operation across the width of the machine. To rephase the cylinders, the machine normally must be fully raised, which results in loss of time and operating efficiency. Other systems rely on mechanical depth stops to control operating height, but do not allow the operator to change that height from the cab or to easily vary depth for different transport conditions, ground contours and soil conditions. In addition, both the series cylinder and the mechanical depth stop systems require mechanical adjustment outside the cab to adjust the height of wing frames relative to the main or center frame. Adequate level control for fore-and-aft frame leveling or tilt and for leveling from side to side have presented problems.
On implement frames with a main frame and individual wing sections, depth of penetration of the wing sections often varies from that of the main frame, but the cylinder arrangement fails to accommodate easy and reliable adjustments of the wing sections relative to the main frame. Wing section cylinder stroke and size sometimes is determined by the cylinder matching requirements of the hydraulic system rather than by lift capacity and space considerations so that the cylinders are not optimal or most economical.